Accession Number : ADA289546

Title :   Nitride Semiconductors for Ultraviolet Detection.

Descriptive Note : Semiannual technical rept. for 1 Jul 94-31 Dec 94,

Corporate Author : NORTH CAROLINA STATE UNIV AT RALEIGH

Personal Author(s) : Davis, R. F. ; Linthicum, K. ; Perry, B. ; Smith, L. ; Weeks, W.

PDF Url : ADA289546

Report Date : 31 DEC 1994

Pagination or Media Count : 43

Abstract : Monocrystalline, undoped, high resistivity GaN thin films have been grown on (6H)-SiC(0001) wafers via organometallic vapor phase epitaxy (OMVPE) employing a high-temperature monocrystalline AlN buffer layer using a cold-wall, vertical pancake-style reactor with triethylgallium (TEG), triethylaluminum (TEA) and ammonia. The surface morphologies of films deposited on both vicinal and on-axis, Si- and C-polar planes of SiC(0001) are described. Controlled n-type Si-doping in GaN has been achieved with carrier concentrations from 10(exp 17) to 10(exp 20)/ cu cm. SEM and TEM of the latter films revealed high microstructural quality Photoluminescence (PL) of the undoped GaN revealed a sharp donor-bound exciton peak at 357.2 nm with a FWHM of 4 meV. The defect peaks in these samples were very weak. The Si-doped GaN exhibited a strong PL emission at 358 nm due to donor-to-valence band transitions. Mg-doped GaN emitted strong blue light with a peak wavelength of 426 nm. Cathodoluminescence measurements of Al(x)Ga(1-x)N were also successful, with strong emission at the band-edge. An ammonia cracker cell, has also been designed and installed in the gas source MBE to replace the ECR plasma source to minimize film damage and to enhance film quality and growth rate. Low resistivity Al, Cu3Ge, and TiN ohmic contacts have been achieved on Si-doped, n-type GaN. Au and a Au/Mg/Au layered structure exhibited ohmic behavior on p-GaN when annealed at high temperature or in the as-deposited condition, respectively. As-deposited Pt formed ohmic contacts to Mg:GaN. Microstructural characterization of the Al/n-GaN and Au/p-GaN contact systems revealed that interfacial reactions occurred during annealing and markedly affected contact performance.

Descriptors :   *SEMICONDUCTORS, *NITRIDES, *ULTRAVIOLET DETECTION, BUFFERS, SOURCES, MAGNESIUM, ANNEALING, MICROSTRUCTURE, DAMAGE, INTERFACES, LAYERS, GROWTH(GENERAL), HIGH TEMPERATURE, PLASMAS(PHYSICS), RESISTANCE, PHOTOLUMINESCENCE, MORPHOLOGY, THIN FILMS, LIGHT, FILMS, RATES, CHARGE CARRIERS, ORGANOMETALLIC COMPOUNDS, EPITAXIAL GROWTH, VAPOR PHASES, MOLECULAR BEAMS, AMMONIA, GASES, SURFACES, QUALITY, COPPER, ALUMINUM, GALLIUM, TITANIUM, CATHODOLUMINESCENCE, GOLD, BLUE(COLOR), GERMANIUM, SILICON CARBIDES, ETHYL RADICALS, ELECTRIC CONTACTS, TRIETHYLALUMINUM.

Subject Categories : Inorganic Chemistry
      Electrical and Electronic Equipment
      Optics

Distribution Statement : APPROVED FOR PUBLIC RELEASE